Vermont casting Encore flex burn over firing?

[NHwoodstover]

I have a Vermont casting encore 2n1 flexburn, I’m running it without the cat as I can’t get them to last more than a season (they melt pretty bad, even though I installed an Auber AT100 with a cat temp probe and I never let it go over 1500F), and I’m burning kiln dried hardwood (mostly oak) which measures <8% moisture content.

I previously had a cracked fireback and fire top and got new ones under warranty from VC, which I fitted myself and did a full rebuild with new gaskets everywhere. I’ve tested and can’t find any obvious air leaks, today I pulled the stove out remove the flue collar and fitted a new 30002422 3/8” fiberglass gasket, took the bottom off the T and gave the chimney pipe a good bash. There was little to no creosote in the bottom of the T, and I looked up the chimney and it looked visibly clear (I did not sweep it, it was last swept at the end of last season and I’ve put almost 4 cords through it this season). The chimney is a very tall brick chimney (40ft and change) with a steel flex pipe liner, Un-insulated currently. The stove is 5 seasons old.

My problem is if I run the stove with the damper open I immediately get the roaring air sound and the T and the flex pipe goes dull to cherry red (700+F). If I close the damper the roar goes away immediately and the pipe returns to a sensible temp. The stove isn’t even that hot when it does this, it can happen with griddle temps in the 4-500F range. It really looks like a chimney fire, but I can turn it on and off with the damper, and surely if it was a chimney fire it would have burnt away the creosote by now? I visually inspected the chimney cap and there are no visible flames or sparks coming out when the T is cherry red.

I can also crank the air down to minimum with the damper closed and get an all night burn without any issues, I load it up about 9-10pm and I still have plenty of coals at 7am for it to relight easily just by putting new wood in.

So….what am I doing wrong? Is it some air leak I haven’t found? Is my wood too dry? (Is that possible?). Should I invest in a higher quality insulated liner?

We love the stove’s heat, but damn this thing is high maintenance, I’m kind of tired of babysitting it and I’m afraid to let my wife run it by herself when I’m away. If it wasn’t for the cherry red chimney and the roaring air id think it was running great.

The picture attached are from a burn I just did now, within 10-15mins of starting it with the damper open I got the red stove pipe, I then closed the damper and it went away, re-opened the damper and red pipe again. Included infrared thermometer pics are all from when the pipe was glowing. I closed the damper even though the stove wasn’t very hot and the temp in the cat area shot up but isn’t crazy, as shown by the Auber pic. I then turned the air down to minimum and it’s calmed down and seems to be in cruise mode, 600F griddle top currently which I find will drop to about a stable 450F after an hour or so, with most the flames gone, which is the second pic of the fire.

Appreciate any advice!

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[bholler]

I have a Vermont casting encore 2n1 flexburn, I’m running it without the cat as I can’t get them to last more than a season (they melt pretty bad, even though I installed an Auber AT100 with a cat temp probe and I never let it go over 1500F), and I’m burning kiln dried hardwood (mostly oak) which measures <8% moisture content.

I previously had a cracked fireback and fire top and got new ones under warranty from VC, which I fitted myself and did a full rebuild with new gaskets everywhere. I’ve tested and can’t find any obvious air leaks, today I pulled the stove out remove the flue collar and fitted a new 30002422 3/8” fiberglass gasket, took the bottom off the T and gave the chimney pipe a good bash. There was little to no creosote in the bottom of the T, and I looked up the chimney and it looked visibly clear (I did not sweep it, it was last swept at the end of last season and I’ve put almost 4 cords through it this season). The chimney is a very tall brick chimney (40ft and change) with a steel flex pipe liner, Un-insulated currently. The stove is 5 seasons old.

My problem is if I run the stove with the damper open I immediately get the roaring air sound and the T and the flex pipe goes dull to cherry red (700+F). If I close the damper the roar goes away immediately and the pipe returns to a sensible temp. The stove isn’t even that hot when it does this, it can happen with griddle temps in the 4-500F range. It really looks like a chimney fire, but I can turn it on and off with the damper, and surely if it was a chimney fire it would have burnt away the creosote by now? I visually inspected the chimney cap and there are no visible flames or sparks coming out when the T is cherry red.

I can also crank the air down to minimum with the damper closed and get an all night burn without any issues, I load it up about 9-10pm and I still have plenty of coals at 7am for it to relight easily just by putting new wood in.

So….what am I doing wrong? Is it some air leak I haven’t found? Is my wood too dry? (Is that possible?). Should I invest in a higher quality insulated liner?

We love the stove’s heat, but damn this thing is high maintenance, I’m kind of tired of babysitting it and I’m afraid to let my wife run it by herself when I’m away. If it wasn’t for the cherry red chimney and the roaring air id think it was running great.

The picture attached are from a burn I just did now, within 10-15mins of starting it with the damper open I got the red stove pipe, I then closed the damper and it went away, re-opened the damper and red pipe again. Included infrared thermometer pics are all from when the pipe was glowing. I closed the damper even though the stove wasn’t very hot and the temp in the cat area shot up but isn’t crazy, as shown by the Auber pic. I then turned the air down to minimum and it’s calmed down and seems to be in cruise mode, 600F griddle top currently which I find will drop to about a stable 450F after an hour or so, with most the flames gone, which is the second pic of the fire.

Appreciate any advice!

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If you have a 40' tall chimney you are probable 3 or 4x the specified draft so yeah it's going to over fire. You need atleast 1 damper in the pipe probably more.

 

[bholler]

And that isn't how you use a moisture meter. You need to re split the wood then take a reading on the fresh face

 

[NHwoodstover]

Thanks for the quick reply! I’ll split a log and test inside.

I may be over estimating the the height, but the house is three floors with 10’ ceilings so it’s at the least 30’. I’ve been running the stove like this for almost 5 full seasons now so I’m kinda pissed my installer didn’t tell me I’d need additional dampers, is this a dangerous situation? I don’t remember the stove pipe glowing red like this as easily on previous seasons. I presume these dampers go in the stove pipe itself? How do you control them?

 

[NHwoodstover]

And that isn't how you use a moisture meter. You need to re split the wood then take a reading on the fresh face

Split a couple of logs, looks like they are between 15-17% moisture content.

 

[bholler]

Split a couple of logs, looks like they are between 15-17% moisture content.

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Still very good. Your problem is over draft

 

[EbS-P]

If it’s glowing it’s well above 600. Probably close to 1000 if not higher. Glowing is never good. Is it safe??? It makes me nervous. Integrity of the flex liner that’s been that hot would be my worry. Get a damper or restrict the air intake in some way.

 

[ratsrepus]

try a damper as B holler advised, if that doesnt work a trip to the scrap yard might be in order. Everyone that I know including myself have had nightmares with the VC brand. I gave up on mine after 5 years.

 

[ABMax24]

Another note, infrared temp guns have a spot size, many are 10:1, so at 10ft away they measure the average of a 1ft circle, it looks like yours is measuring the background around that connector and averaging it, there's no way that glowing red connector is only 558F. They also have a max temperature they read to, mine goes to 800F accurately but will read to 850F, some models are much lower than this.

As has already been said, overdraft is your primary issue, its the reason your catalysts melt, the stove internals are cracking, and why the chimney glows red.

 

[NHwoodstover]

Thanks for the replies guys. Yeah I figured my IR gun wasn’t reading the glowing pipe temp correctly, it’s a cheap RadioShack one it caps out at 750F then just reads “Hi” which is what I expected it to read.

If I run the stove with the damper shut all the time except when loading and the first 5-10mins of starting a fire, I don’t get the red stove pipe. But as ABMax said I’m eating internal components every season so I know it’s too hot in there. I also have to be careful about shutting down the air too quickly when I do have the damper closed else I get back puffing. What a pain this stove is!

Maybe it’s time to accept this stove just isn’t any good rather than constantly throwing money and time at it replacing parts. Sad because it’s not very old, it looks great, I love the top load, and it kicks out a ton of heat, but it’s not worth the risk of a house fire or something.

I wonder if it’s safe to nanny to the end of the season? Only 3-4 weeks left before we won’t need it anymore, I have about a cord of wood left and it saves me so much money on oil, especially with the current prices.

Side question; what would be a recommended equivalently sized stove with a similar heat output that doesn’t have all these issues? I’m looking to avoid anything with a cat.

 

[MMH]

Quickly glancing through your manual it’s recommended minimum 16’, so your at least double that (tacking onto the overdraft wagon). Cherry red pipe is never good, as mentioned by others. You've mentioned this has happened numerous times, and with the pipe getting that hot (god only knows what the actual temps have been) this can compromise the integrity of the pipe which isn’t safe (fire, CO etc) so personally I wouldn’t use it, and my 2 cents would be to stop, at least until it has been THOROUGHLY inspected. As for your side question of what to replace it with, I would look at lopi or PE.